The present invention relates to an incylinder direct injection spark ignition engine.
An incylinder direct injection spark ignition engine is generally arranged to perform stratified charge combustion in a preset engine operating region, by utilizing incylinder fluid flow in a combustion chamber to covey injected fuel to the vicinity of a spark plug for ignition. Published Japanese Patent Application, Publication (Kokai) No. 2000-87750 discloses such a direct injection engine.
In a low engine speed light engine load region, the quantity of intake air is so small that tumble in a combustion chamber is too weak to carry injected fuel adequately to the vicinity of a spark plug, and to achieve stratified charge combustion satisfactorily.
It is therefore an object of the present invention to provide a direct injection spark ignition engine capable of providing stable stratified charge combustion even in the low speed light load engine operating region.
According to the present invention, an incylinder direct injection spark ignition engine comprises: a cylinder block comprising a cylinder bore; a cylinder head comprising a depression defining an upper inside surface of a combustion chamber; a spark plug projecting from the upper surface of the combustion chamber; a piston which is received in the cylinder bore to reciprocate in the cylinder bore, which comprises a piston crown which forms the combustion chamber with the depression of the cylinder head, and which is formed with a cavity; first and second intake ports opened in the upper surface of the combustion chamber, and designed to introduce intake air toward the piston so as to create tumble in cooperation with the cavity; an incylinder fluid motion control device which is to be operated in a first engine operating region, to promote the tumble in the combustion chamber so that injected fuel is conveyed to the spark plug by the tumble; and a fuel injector which is positioned, between the first and second intake ports, at a position lower than the first and second ports, which is arranged to inject fuel directly into the combustion chamber toward the center of the combustion chamber on compression stroke, and to produce a fuel spray penetrating the vicinity of the spark plug in a second engine operating region which is a low speed light load region.
According to another aspect of the present invention, an incylinder direct injection spark ignition engine comprises: an engine block (such as an assembly of cylinder block and head) comprising a cylinder bore, and a depression defining an upper inside surface of a combustion chamber; a spark plug located in a center region of the upper inside surface into the combustion chamber; a piston comprising a cylindrical portion to reciprocate in the cylinder bore and a piston crown formed with a cavity; at least one intake port which is opened in an intermediate region of the upper inside surface of the combustion chamber located radially between the central region and a peripheral region of the upper inside surface of the combustion chamber, and which is designed to introduce intake air toward the piston so as to create tumble in cooperation with the cavity; a tumble control valve provided in said one intake port, and arranged to move between an operative state to promote the tumble in the combustion chamber to convey injected fuel to the spark plug by the tumble to achieve a first stratified charge combustion mode, and an inoperative state to restrain the tumble in the combustion chamber to achieve a second stratified charge combustion mode in a low engine speed light engine load operating region; and a fuel injector located in the peripheral region of the upper inside surface of the combustion chamber, and configured to produce a fuel spray spreading in the form of a cone bounded between a lowermost line directed to the cavity of the piston crown and an uppermost line aimed at the spark plug in the second stratified charge combustion mode.
According to still another aspect of the present invention, an incylinder direct injection spark ignition engine comprises: igniting means for igniting an ignitable air fuel mixture cloud when the air fuel mixture cloud reaches a spark region in a combustion chamber of the engine; tumble producing means for producing tumble in the combustion chamber by introducing intake air into the combustion chamber in a first stratified charge combustion mode, and restraining the tumble in a second stratified charge combustion mode; and injecting means for injecting fuel into the combustion chamber in a direction to avoid interference with the spark region, and thereby producing a fuel spray comprising an upper segment which reaches the spark region in the second stratified charge combustion mode.
The other objects and features of this invention will become understood from the following description with reference to the accompanying drawings.